The GDK Card
class does not have functionality to alter the color of text, reference here: https://developers.google.com/glass/develop/gdk/reference/com/google/android/glass/app/Card
However, you can alter text color in your style. Add a line in res/values/styles.xml within your <style>
object
<item name="android:textColor">#00FF00</item>
More information on styles and themes here: http://developer.android.com/guide/topics/ui/themes.html